a provocative article in the NY Times projects the possibility that genetics predisposes some - esp women - to NON-CONTACT anterior cruciate ligament (ACL) tears. http://well.blogs.nytimes.com/2010/09/29/phys-ed-are-bad-knees-in-our-genes/?ref=health
tim hewett, of cincinnati children's hospital, a prominent researcher on ACL injury and prevention, reports that one set of twin girls tore their knees up within a year. their older sister also tore her ACL. another set of twin sisters had incurred torn ACLs in high school, as did their dad...and his two triplet brothers!!!! scary huh? suggesting that you can look at your family's knees and see your risk profile in scar tissue.
studies in south africa have found a gene sequence that alters the customary elasticity of ligamentous collagen. interestingly, more women had this aberration whereas males who had had ACL injuries did not have this variant and women who had not torn their ACLs also did not have it.
so, we can now add to the list of predisposing factors - weak, easily-fatiguing, and late-firing hamstrings; weak and delayed-firing gluteus medii; possible femoral notch anatomical variations; and poor training/jumping/cutting technique - genetics. like many things genetics, this does not mean you WILL have an ACL tear if other family members have had one. but it does mean you might want to train properly with more closed chain- squats and lunges - and plyometric - jumping/hopping - and agility - cutting, changing direction - exercises. see a pro who's studied this syndrome, not just one who knows how to build bigger muscles. you need better ones, not bigger ones.